In a communication switch, a switch fabric is provided. The switch fabric may be implemented as a conventional cell space switch whereby cells are received at any of N input ports and switched to any of N output ports through a connection. The design of such fabrics are rather simple, and typically include buffering at each output port. Buffering within the fabric may not be adequate, depending on demands from periphery subsystems, resulting in loss of data cells at the fabric.
Backpressure is a well-known feedback technique to reduce or prevent cell loss when the switch fabric experiences congestion. The fabric sends a Backpressure Indication (feedback message) for a congested output port to the peripheral subsystem, which in response holds back sending cells destined to that port. Typically all input ports which are connected to the output port receive the same backpressure signal. Accordingly it is desirable to minimize the need for backpressure signalling.
For example, in a typical N×N switching architecture, the use of backpressure would allow congestion in the switching fabric to “push-back” to the input port. When an input port receives a backpressure indication from an output port, the input port stops sending data transmissions to the output port. While Quality of Service (QoS) standards for transmission rates are ensured using backpressure signalling, the use of backpressure signalling is disruptive to the traffic flow for an input port.
There is a need for a system and method for regulating cell traffic to reduce the generation I/O of backpressure signals that improves upon prior art systems.